1. Field of the Invention
The present invention discloses a key device for a computer keyboard. More particularly, the key circuit of the computer keyboard is made from a rigid printed circuit board.
2. Description of the Prior Art
Please refer to FIG. 1 and FIG. 2. FIG. 1 is a schematic diagram of a known computer keyboard 10. A sectional view along line 2xe2x80x942 of the computer keyboard 10 is shown in FIG. 2. The computer keyboard 10 has a plastic housing 12 and a plurality of key devices 14 fixed inside the plastic housing 12.
The key device 14 includes two stacked flexible printed circuit board 16, and 18. The bottom surface 20 of the upper flexible printed circuit board 16, and the upper surface 22 of the lower flexible printed circuit board 18 each have a conductive segment 24 and 26 respectively. A soft plastic segment 28 is installed between the two printed circuit boards 16, 18. A metal plate 13 is installed on the printed circuit board 16. A supporting plate 17 is installed under the printed circuit board 18 to provide the supporting force needed for pushing the key device 14. The soft plastic segment 28 has a hole 30 positioned between the conductive segments 24, 26, and the hole 30 makes a gap between the conductive segments 24, 26.
The key device 14 further includes a keycap 32, a scissors-like support 34 that is moveable in up and down directions to fix the keycap 32 onto the flexible printed circuit board 32. An elastic component 36, installed between the keycap 32 and the flexible printed circuit board 16, upwardly supports the keycap 32 in an elastic manner. When the keycap 32 is pushed downward, the bottom surface of the elastic component 36 will touch the conductive segment 24 of the flexible printed circuit board 16, causing the conductive segment 24 to form an electrical connection with the conductive segment 26 of the flexible printed circuit board 18.
Please refer to FIG. 3. FIG. 3 is a schematic diagram of the partial structure of another key device 40 according to the prior art for a computer keyboard 10. The key device 40 includes two stacked flexible printed circuit boards 42 and 44, which are adhered together. Isolation layers 54 and 56 are installed on the flexible printed circuit boards 42 and 44, respectively. The isolation layers 54 is printed on the bottom surface 46 of the flexible printed circuit board 42, and the isolation layer 56 is printed on the upper surface 48 of the flexible printed circuit board 44. The isolation layers 54, 56 encircle the conductive segments 50 and 52, respectively. Because the isolation layer 54 protrudes from the bottom surface 46 of the flexible printed circuit board 42, and the isolation layer 56 protrudes from the upper surface 48 of the flexible printed circuit board 44, the thickness of the two isolation layers 54 and 56 creates a gap between the two conductive segments 50 and 52.
Because of their flexible nature, decoders cannot be soldered onto the flexible printed circuit boards 16, 18 and 42, 44. Therefore, the computer keyboard 10 can not produce decoded key signals. Instead, it must be connected to a decoding circuit (not shown) through signal lines to produce the corresponding decoded key signals. Furthermore, the supporting plate 17 is used only to provide the supporting force needed to push the key device 14.
It is therefore an objective of the present invention to provide a key device that uses a rigid printed circuit board to solve the above-mentioned problems.
Briefly, the present invention provides a way to combine a rigid printed circuit board and a flexible printed circuit board together to form a different key device upon which can be soldered a decoder. The computer keyboard can thus produce decoded key signals without the use of an external decoding circuit.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment, which is illustrated in the various figures and drawings.